The unique stamps that stick without licking

January 28th, 2015 would like to share with our readers interesting info. Did you know that getting stamps to stick hasn't always been a simple task.

Most stamps made after 1840 came with an adhesive gum on the back. But the gum‒made from various plant products such as cornstarch, sweet potatoes, gum Arabic, and sugar‒wasn't always of the highest quality, meaning stamps often fell off letters. The U.S. Postal Service tried various gum formulas to remedy the situation, including special "summer gum" that was resistant to humidity, and "winter gum" that resisted cracking in cold, dry winter air.

Finally, in the 1960s, the South Pacific island kingdom of Tonga broke the mold when it printed a series of self-adhesive stamps. Not only did they not require licking, they came in odd shapes‒the most famous of which was this 1969 stamp (below) shaped like a banana. These unusual stamps were a big hit and, for a time, became a significant source of revenue for the country.

Collectors went crazy for them. In fact, they became so popular that one dealer ordered more copies of a particular stamp than had been printed. Most countries followed Tonga's lead, and today, the die-cut, peel-and-stick stamps are the most common type of stamps in the United States.